while-loop

When I am reading a file sample script while read file do temp = $(echo $file) read -p "Press Enter to continue" echo $temp done < test.txt I want to pause the script until I press ENTER read reads from standard input by default, which is redirected to the file, so it's getting the line from the file. You can redirect back to the terminal: read -p "Press Enter to continue" </dev/tty Another option would be to use a different FD for the file redirection while read -u 3 do ... done 3< test.txt 来源： https://stackoverflow.com/questions/35075364/pause-shell-script-until-press-enter-in-while-loop

Python has an elegant way of automatically generating a counter variable in for loops: the enumerate function. This saves the need of initializing and incrementing a counter variable. Counter variables are also ugly because they are often useless once the loop is finished, yet their scope is not the scope of the loop, so they occupy the namespace without need (although I am not sure whether enumerate actually solves this). My question is, whether there is a similar pythonic solution for while loops. enumerate won't work for while loops since enumerate returns an iterator. Ideally, the solution

I would like to know if / how it is possible to parallelize a while loop in R. If it is not possible or reasonably considered too difficult to accomplish, I would greatly appreciate an alternative, possibly using a parallel for loop instead. You can use futures with any looping R construct including for() and while() loops. Futures are implemented in the future package (I'm the author). It is not clear what condition you want to use for your while loop. That would have helped give a more precise answer. Here is an example where the while condition does not depend on any of the results

Trying to find unique ID in Node.js and MongoDB, by creating a while loop that queries MongoDB for existing IDs, until a unique value is found. If the ID is already in use, a number is incremented on the end until Mongo returns nothing. Everything is working, except for the break; statement when a unique ID is found. Node.js returns: SyntaxError: Illegal break statement The code: db.collection('landmarks').findOne({'id':uniqueIDer}, function(err, data){ //if ID exists already if (data.id){ var uniqueNumber = 1; while (1) { var uniqueNum_string = uniqueNumber.toString(); var newUnique = data.id

When I compile and run this code (it's part of a much larger program), Linux gets halfway through the while loop, then simply stops working. The code below prints time: 0 and then hangs, doing nothing else until I suspend the process. Why on earth would it print time: 0 but not the following line of sanity check? while (i < 5) { printf("time: %d\n",elapsedTime); printf("sanity check"); foo(); i++; } Output usually is buffered and only written after a flush or newline. In printf("sanity check"); there is no newline, so if you run in an endless loop after this, you won't see it. Replace it with

In Java it is possible to declare a variable in the initialization part of a for -loop: for ( int i=0; i < 10; i++) { // do something (with i) } But with the while statement this seems not to be possible. Quite often I see code like this, when the conditional for the while loop needs to be updated after every iteration: List<Object> processables = retrieveProcessableItems(..); // initial fetch while (processables.size() > 0) { // process items processables = retrieveProcessableItems(..); // update } Here on stackoverflow I found at least a solution to prevent the duplicate code of fetching the